Substitution and hydrogenation reactions on rhodium(I)-ethylene complexes of the hydrotris(pyrazolyl)borate ligands T (T = Tp, TpMe2)

The bis(ethylene) Rh species TpMe2Rh(C2H4)2(1*) (TpMe2 = tris(3,5-dimethyl-1-pyrazol-1-yl)hydroborate) has been obtained from [RhCl(C2H4)2]2 and KTpMe2. Complex 1* easily decomposes in solution to give mainly the butadiene species TpMe2Rh(eta74-C4H6). In the solid state its thermal decomposition follows a different course and the allyl TpMe2RhH(syn-C3H4Me) is cleanly obtained as a mixture of exo and endo isomers. The complexes Tp'Rh(C2H4)2 (Tp' = Tp, TpMe2) afford the monosubstituted species Tp'Rh(C2H4)(PR3) upon reaction with PR3 but react differently with L = CO or CNR: the Tp compound gives dinuclear [TpRh]2(mu-L)3 complexes, while, in the case of 1*, TpMe2Rh(C2H4)(L) species are obtained. The ethylene ligand of complexes TpMe2Rh(C2H4)(PR3) is labile, and several peroxo compounds of composition TpMe2Rh(O2)(PR3) have been isolated by their reaction with O2. All the mononuclear Rh(I) complexes are formulated as 18e- trigonal bipyramidal species on the basis of IR and NMR spectroscopic studies. A series of dihydride complexes of Rh(III) of formulation Tp'RhH2(PR3) have been prepared by the hydrogenation of the corresponding ethylene derivatives. Complexes [TpRh]2(mu-CNCy)3, TpMe2Rh(C2H4)(PEt3), and TpMe2Rh(O2)(PEt3) have been further characterized by X-ray diffraction studies.

Denticity Changes of Hydrotris(pyrazolyl)borate Ligands in Rh(I) and Rh(III) Compounds: From kappa(3)- to Ionic "kappa(0)"-Tp'

Isolated hydrotris(pyrazolyl)borate anions Tp' were obtained as salts of metal complex cations (see picture) by the displacement of Rh-coordinated kappa(3)-N,N',N"-Tp' by PMe(3) (Tp'=Tp and Tp(Me2)). With [(kappa(3)-Tp(Me2))Rh(C(2)H(4))(2)], stepwise diplacement of the Tp(Me2) ligand allowed the isolation of complexes exhibiting the kappa(2)- Tp(Me2) and kappa(1)-Tp(Me2) coordination modes.

Acute mania: haloperidol dose and augmentation with lithium or lorazepam

Antipsychotic dosing for acute mania has not been well studied. Combined treatment with lithium and an antipsychotic is the most common treatment, but additional antimanic efficacy of a lithium-antipsychotic combination beyond that of an antipsychotic alone has not been well demonstrated. Furthermore, the possibility that lithium could affect antipsychotic dose requirement is believed to have never been studied. In this study, 63 acutely psychotic bipolar manic inpatients were randomly assigned to receive double-blind treatment with 1 of 2 haloperidol doses, 25 mg/day or 5 mg/day, for 21 days. In addition to haloperidol, subjects were randomly assigned to receive concomitant treatment with placebo, standard lithium, or lorazepam 4 mg/day. The high haloperidol dose produced greater improvement and more side effects than did the low dose. Lithium added to the low dose produced a markedly greater clinical response than did the low dose alone. Lorazepam did not improve the outcome for the patients receiving low-dose haloperidol. The clinical response produced by high-dose haloperidol was not enhanced by adding either lithium or lorazepam. All treatment effects emerged by the fourth day of treatment and persisted. Used alone, a haloperidol dose of 5 mg/day is too low for most manic patients, but concomitant lithium produces a dose-dependent enhancement of haloperidol response. Lorazepam 4 mg/day was insufficient to produce an advantage when added to low-dose haloperidol.

Mutation analysis of the RPGR gene reveals novel mutations in south European patients with X-linked retinitis pigmentosa

The RPGR (retinitis pigmentosa GTPase regulator) gene has been shown to be mutated in 10-20% of patients with X-linked retinitis pigmentosa (XLRP), a severe form of inherited progressive retinal degeneration. A total of 29 different RPGR mutations have been identified in northern European and United States patients. We have performed mutation analysis of the RPGR gene in a cohort of 49 southern European males affected with XLRP. By multiplex SSCA and automatic direct sequencing of all 19 RPGR exons, seven different and novel mutations were identified in eight of the 49 families; these include three splice site mutations, two microdeletions, and two missense mutations. RNA analysis showed that the three splice site defects resulted in the generation of aberrant RPGR transcripts. Six of these mutations were detected in the conserved amino-terminal region of RPGR protein, containing tandem repeats homologous to the RCC1 protein, a guanine nucleotide-exchange factor for Ran-GTPase. Several exonic and intronic sequence variations were also detected. None of the RPGR mutations reported in other populations were identified in our series. Our results are consistent with the notions of heterogeneity and minority causation of XLRP by mutations in RPGR in Caucasian populations.

Tachykinin receptor and neutral endopeptidase gene expression in the rat uterus: characterization and regulation in response to ovarian steroid treatment

Tachykinin neuropeptides, such as substance P, are localized to a population of sensory fibers that innervate the mammalian female reproductive tract. In the present study, we have characterized tachykinin NK1 receptor (NK1R), NK2 receptor (NK2R), and NK3 receptor (NK3R) gene expression by semiquantitative RT-PCR in uteri from ovariectomized rats and studied their regulation in response to 17beta-estradiol (E2), progesterone (P4), or a combination of both. In addition, we analyzed the expression and regulation of the neutral endopeptidase 24.11 (NEP), the most important enzyme involved in tachykinin degradation in the rat uterus. In uteri from control (olive oil-treated) rats, RT-PCR assays revealed single bands corresponding to the expected product sizes encoding complementary DNA for NK1R (232 bp), NK2R (491 bp), NK3R (325 bp), and NEP (221 bp). The identity of the amplified fragments was confirmed by DNA sequence analysis. Compared with control rats, NK1R messenger RNA (mRNA) was increased by 2-fold in uteri from rats treated with E2, was decreased by 3.3-fold in rats treated with P4, and was decreased by 1.8-fold in rats treated with both E2 and P4. Uterine NK2R mRNA levels were not altered by any steroid treatment. E2 treatment decreased by 15-fold NK3R mRNA. P4 was without effect if administered alone and did not influence the E2-induced decrease in NK3R mRNA. NEP mRNA levels were about 4-fold lower in E2-treated than in P4-treated rats. Functional studies were carried out in uteri from E2- or P4-treated ovariectomized rats to characterize the contractile response evoked by the selective tachykinin receptor agonists [Sar9Met(O2)11]substance P (NK1R selective), [Nle10]NKA-(4-10) (NK2R selective), and [MePhe7]NKB (NK3R selective) in the presence of the NEP inhibitor phosphoramidon (1 microM). A marked correlation was observed between the magnitude of the contractile response to each agonist and the level of expression determined by RT-PCR for each tachykinin receptor. The present findings show that tachykinin NK1R, NK2R, NK3R, and NEP are expressed in the rat uterus and that ovarian steroids differentially regulate their expression.

Pharmacodynamics of vancomycin for the treatment of experimental penicillin- and cephalosporin-resistant pneumococcal meningitis

With the emergence of beta-lactam antibiotic resistance among strains of Streptococcus pneumoniae, vancomycin has assumed an important role in the treatment of bacterial meningitis. Using the rabbit meningitis model, we evaluated the pharmacokinetics and pharmacodynamics of vancomycin in this setting. Animals were given 80 mg/kg of body weight daily in two or four divided doses to determine the penetration and activity of vancomycin in cerebrospinal fluid (CSF); each regimen was administered with and without dexamethasone. Mean peak (2 h) concentrations in CSF that were four- to eightfold higher than the minimum bactericidal concentration (MBC; 0.5 microgram/ml) for the pathogen were adequate for bacterial clearance. In both groups concentrations in CSF remained higher than the MBC for greater than 80% of the respective dosing intervals, and the penetration of vancomycin into CSF was 20%. Mean concentrations in CSF at 24 to 36 h of therapy were lower than those achieved during the first 12 h, consistent with a decline in the level of antibiotic entry into CSF as inflammation wanes. Rates of bacterial clearance were similar for the two regimens, and for all animals cultures of CSF were sterile by 36 h. The coadministration of dexamethasone significantly reduced the penetration of vancomycin into CSF by 29% and significantly lowered the rate of bacterial clearance during the first 6 h in animals receiving 20-mg/kg doses of vancomycin. For animals receiving 40-mg/kg doses, therapeutic peak concentrations in CSF were obtained even with steroid use, suggesting that the effect of steroids may be circumvented by the use of larger daily doses of vancomycin.

Once-daily therapy for H. pylori infection: a randomized comparison of four regimens

OBJECTIVE

We sought to determine the efficacy and tolerability of novel, once-daily therapies in the treatment of Helicobacter pylori infection.

METHODS

One hundred sixty subjects with H. pylori infection documented by endoscopic biopsy or serology plus 13C-urea breath test were randomly assigned to omeprazole 80 mg q.d. and metronidazole extended-release formulation 750 mg q.d. for 10 days (OM); OM plus amoxicillin 1.5 g q.d. for 10 days (OMAm); OM plus azithromycin 500 mg q.d. for 7 days (OMAz); or OM plus clarithromycin 1 g q.d. for 10 days (OMCI). A repeat breath test was done 6 wk after the completion of therapy. Subjects were considered compliant if they took > or = 80% of each study medication as prescribed.

RESULTS

Intent-to-treat eradication rates were OM = 8% (95% confidence interval [CI], 2-20%), OMAm = 35% (95% CI, 21-52%), OMAz = 65% (95% CI, 48-79%), and OMCI = 78% (95% CI, 62-89%). Lack of compliance was seen in 5% of subjects given OM, 8% given OMAm, 3% given OMAz, and 15% given OMCI.

CONCLUSIONS

This pilot study demonstrated that once-daily triple therapy with high-dose omeprazole, metronidazole extended-release formulation, and clarithromycin achieved an eradication rate approaching 80%. Further study may permit development of optimal once-daily dosing and enhance eradication rates.

Etiology and treatment of community-acquired pneumonia in ambulatory children

OBJECTIVES

To determine the etiology of community-acquired pneumonia in ambulatory children and to compare responses to treatment with azithromycin, amoxicillin-clavulanate or erythromycin estolate.

METHODS

Ambulatory patients with pneumonia were identified at the Children's Medical Center of Dallas, TX. Children age 6 months to 16 years with radiographic and clinical evidence of pneumonia were enrolled and randomized to receive either azithromycin suspension for 5 days or a 10-day course of amoxicillin-clavulanate for those <5 years or erythromycin estolate suspension for those > or = 5 years. Blood culture was obtained in all patients and we obtained nasopharyngeal and pharyngeal swabs for culture and polymerase chain reaction (PCR) testing for Chlamydia pneumoniae and Mycoplasma pneumoniae and nasopharyngeal swabs for viral direct fluorescent antibody and culture. Acute and convalescent serum specimens were tested for antibodies to C. pneumoniae, M. pneumoniae and Streptococcus pneumoniae. Patients were evaluated 10 to 37 days later when repeat specimens for serology, PCR and culture were obtained. For comparative purposes healthy children attending the well-child clinic had nasopharyngeal and pharyngeal swabs obtained for PCR and culture for C. pneumoniae and M. pneumoniae.

RESULTS

Between February, 1996, and December, 1997, we enrolled 174 patients, 168 of whom fulfilled protocol criteria for evaluation. There were 55% males and 63% were <5 years of age. All blood cultures were sterile and there was no correlation between the white blood cell and differential counts and etiology of pneumonia. Etiologic agents were identified in 73 (43%) of 168 patients. Infection was attributed to M. pneumoniae in 7% (12 of 168), C. pneumoniae in 6% (10 of 168), S. pneumoniae in 27% (35 of 129) and viruses in 20% (31 of 157). None of the swab specimens from 75 healthy control children was positive for C. pneumoniae or M. pneumoniae. Clinical response to therapy was similar for the three antibiotic regimens evaluated, including those with infection attributed to bacterial agents.

CONCLUSION

Although a possible microbial etiology was identified in 43% of the evaluable patients, clinical findings and results of blood cultures, chest radiographs and white blood cell and differential counts did not distinguish patients with a defined etiology from those without a known cause for pneumonia. There were no differences in the clinical responses of patients to the antimicrobial regimens studied.

Effect of proton-pump inhibitor therapy on diagnostic testing for Helicobacter pylori

BACKGROUND

Proton-pump inhibitor therapy may cause false-negative results on Helicobacter pylori diagnostic testing.

OBJECTIVE

To determine the frequency and duration of conversion of urea breath test results from positive to negative in patients given a proton-pump inhibitor.

SETTING

Two urban university gastroenterology clinics.

PATIENTS

Patients infected with H. pylori who had positive results on urea breath tests.

INTERVENTION

Lansoprazole, 30 mg/d for 28 days.

MEASUREMENTS

The urea breath test was repeated at 28 days. If the results were negative, testing was repeated 3, 7, 14, and 28 days after completion of therapy until the results reverted to positive.

RESULTS

31 (33%) of 93 patients in whom H. pylori was not eradicated had a negative breath test result while receiving lansoprazole. The proportions of patients whose breath test results were positive after completion of lansoprazole therapy were 91% (95% CI, 83% to 96%) at 3 days, 97% (CI, 90% to 99%) at 7 days, and 100% (CI, 96% to 100%) at 14 days.

CONCLUSION

Patients should not receive proton-pump inhibitors for 2 weeks before receiving the urea breath test for H. pylori infection.

Xanthine oxidase-mediated decomposition of S-nitrosothiols

S-Nitrosothiols (RSNO) occur in vivo and have been proposed as nitric oxide (.NO) storage and transport biomolecules. Still, the biochemical mechanisms by which RSNO release .NO in biological systems are not well defined, and in particular, the interactions between reactive oxygen species and RSNO have not been studied. In this work, we show that xanthine oxidase (XO), in the presence of purine (hypoxanthine, xanthine) or pteridine (lumazine) substrates, induces S-nitrosocysteine (CysNO) and S-nitrosoglutathione (GSNO) decomposition under aerobic conditions. The decomposition of RSNO by XO was inhibitable by copper-zinc superoxide dismutase, in agreement with the participation of superoxide anion (O-2) in the process. However, while superoxide dismutase could totally inhibit aerobic decomposition of GSNO, it was only partially inhibitory for CysNO. Competition experiments indicated that O-2 reacted with GSNO with a rate constant of 1 x 10(4) M-1.s-1 at pH 7.4 and 25 degreesC. The decomposition of RSNO was accompanied by peroxynitrite formation as assessed by the oxidation of dihydrorhodamine and of cytochrome c2+. The proposed mechanism involves the O-2-dependent reduction of RSNO to yield .NO, which in turn reacts fast with a second O-2 molecule to yield peroxynitrite. Under anaerobic conditions, CysNO incubated with xanthine plus XO resulted in CysNO decomposition, .NO detection, and cysteine and uric acid formation. We found that CysNO is an electron acceptor substrate for XO with a Km of 0.7 mM. In agreement with this concept, the enzymatic reduction of CysNO by XO was inhibitable by oxypurinol and diphenyliodonium, inhibitors that interfere with the catalytic cycle at the molybdenum and flavin sites, respectively. In conclusion, XO decomposes RSNO by O-2-dependent and -independent pathways, and in the presence of oxygen it leads to peroxynitrite formation.

Randomized comparison of ranitidine bismuth citrate-based triple therapies for Helicobacter pylori

OBJECTIVES

In an attempt to increase the efficacy and simplicity of FDA-approved regimens for Helicobacter pylori, we studied (1) addition of an inexpensive antibiotic (amoxicillin) to twice-daily ranitidine bismuth citrate (RBC)-clarithromycin dual therapy, and (2) substitution of RBC for bismuth subsalicylate + H2-receptor antagonist in bismuth-based triple therapy.

METHODS

Subjects with previously untreated Helicobacter pylori infection documented by 13C-urea breath test plus either endoscopic biopsy or serology were randomly assigned to a 2-wk course of (1) RBC 400 mg b.i.d., amoxicillin 1 g b.i.d., and clarithromycin 500 mg b.i.d. (RAC), or (2) RBC 400 mg b.i.d., metronidazole 250 mg t.i.d., and tetracycline 500 mg t.i.d. (RMT). Repeat breath test was performed 4 wk after the completion of therapy.

RESULTS

Intent-to-treat and per-protocol cure rates for RAC were 46 of 50 patients (92%) and 45 of 47 patients (96%); for RMT they were 40 of 50 patients (80%) and 37 of 42 patients (88%). Study drugs were stopped due to side effects in three patients (6%) taking RAC and six patients (12%) taking RMT.

CONCLUSIONS

Twice-daily RBC-based triple therapy with clarithromycin and amoxicillin produces Helicobacter pylori eradication rates over 90%, which is comparable to rates seen with proton pump inhibitor-based triple therapies. RBC also may be substituted for bismuth subsalicylate and an + H2-receptor antagonist in standard bismuth-based triple therapy.

Pharmacodynamics and bactericidal activity of ceftriaxone therapy in experimental cephalosporin-resistant pneumococcal meningitis

Adequate concentrations of beta-lactam antibiotics in cerebrospinal fluid (CSF) are difficult to achieve for meningitis caused by drug-resistant Streptococcus pneumoniae. Ceftriaxone in dosages of 150 or 400 mg/kg of body weight per day, given in one or two doses, was used for the treatment of experimental highly cephalosporin-resistant (MIC and MBC, 4 microg/ml) pneumococcal meningitis. The bacterial killing rate (delta log10 CFU per milliliter per hour) and pharmacokinetic indices, including percentage of time the antibiotic concentration exceeded the MBC during a 24-h period (T>MBC), CSF peak concentration above the MBC, and area under the concentration-time curve from 0 to 24 h above MBC, were measured and correlated. By multiple stepwise regression, only T>MBC independently predicted the bacterial killing rate. There was a direct linear correlation between T>MBC in CSF and the bacterial killing rate during the first 24 h of therapy (r = 0.87; P = 0.004). Sterilization of CSF was achieved only when the T>MBC was 95 to 100%. In the first 24 h, the 200-mg/kg/12-h regimen, compared with the 400-mg/kg/24-h regimen, was associated with a greater T>MBC (87% +/- 10% versus 60% +/- 22%; P = 0.03) and greater bacterial killing rate (0.2 +/- 0.04 versus 0.13 +/- 0.07; P = 0.003), confirming that ceftriaxone exhibits time-dependent bactericidal activity. After 24 h, the T>MBC and the CSF sterilization rates were similar whether ceftriaxone was given once or twice daily.

The effect of interleukin-10 on meningeal inflammation in experimental bacterial meningitis

Interleukin-10 (IL-10) is a cytokine with antiinflammatory effects. In a rabbit model of meningitis, IL-10 was given intracisternally or intravenously to evaluate the impact on inflammation induced by lipooligosaccharide (LOS), Haemophilus influenzae type b (Hib), or Listeria monocytogenes. Intracisternal IL-10 in concentrations >1 microg significantly reduced tumor necrosis factor-alpha (TNF-alpha) and lactate values in cerebrospinal fluid (CSF). Intravenous IL-10 (1 mg/kg) in two doses after intracisternal LOS significantly reduced CSF TNF-alpha and lactate. When Hib was used, animals were treated with ceftriaxone and dexamethasone with or without IL-10 (1 mg/kg). TNF-alpha was significantly reduced in animals treated with IL-10, dexamethasone, or both compared with levels in rabbits receiving ceftriaxone alone. Comparable results were obtained when L. monocytogenes was inoculated and animals were treated with ampicillin with or without IL-10, dexamethasone, or nothing. In conclusion, IL-10 modulates CSF TNF-alpha concentrations in experimental LOS, Hib, or L. monocytogenes meningitis. The maximal inhibitory effect was seen when IL-10 and dexamethasone were combined.

Clinical utility of the polymerase chain reaction for diagnosis of enteroviral meningitis in infancy

OBJECTIVE

To determine the utility of polymerase chain reaction (PCR) assay of cerebrospinal fluid (CSF), serum, and urine for rapid diagnosis of enteroviral meningitis in infants 3 months of age and younger.

STUDY DESIGN

We identified prospectively infants 3 months of age and younger coming to the emergency department with fever whose examination included a lumbar puncture, blood culture, or both. Samples of CSF, serum, urine, throat, and stool specimens were collected for viral culture and, with the exception of stool, for PCR assay. Those infants who had not received prior antibiotic therapy and had sterile bacterial cultures of CSF, blood, and urine were selected for the present analysis.

RESULTS

A total of 259 specimens for viral culture and 203 specimens for PCR assay were collected from 64 infants. Comparison of results of PCR assay of CSF with viral culture, the gold standard for diagnosis of enteroviral meningitis, demonstrated a sensitivity of 100% and a specificity of 90%. Because enteroviruses are not always detectable by culture, the following modified standard was established to define enteroviral meningitis: either CSF pleocytosis, sterile bacterial cultures and detection of an enterovirus in stool culture or positive viral culture of CSF, or both. With this modified definition, the sensitivity and specificity of the PCR assay of CSF were 92% and 94%, respectively. PCR assay of serum and urine offered no benefit over PCR assay of CSF alone for diagnosis of meningitis.

CONCLUSION

PCR assay of CSF is useful for the rapid and reliable diagnosis of enteroviral meningitis. Application of this technique in the clinical setting can potentially diminish unnecessary hospitalization and use of antibiotics.

Assessing sexual dimensions in Hispanic women. Development of an instrument

The purpose of this study was to examine the psychometric properties of a culturally sensitive sexual functioning instrument, the Sexual Dimensions Instrument for Hispanic Women (SDIHW). Using a vignette, the respondent indicated her level of agreement with 26 items that were developed by Hispanic and Anglo nurses/researchers and validated by a panel of clinical and instrument experts. It was translated into Spanish and back-translated; the reading level was at the sixth to seventh grade. The convenience sample consisted of 179 Hispanic women being treated for gynecologic cancer as outpatients. The typical respondent was 35-50 years of age, married, minimally acculturated, religious, and surviving for 1-3 years; she had three or more children, had less than a high-school education, and had little sexual activity in the past month. A three-factor scale with 22 items was determined to have conceptual clarity and moderate reliability (0.63-0.77). Factors included role (eight items), personal sexual satisfaction (eight items), and relationship (six items). The instrument was completed in Spanish by 60% of the respondents. Total and subscale scores were generally not influenced by demographic characteristics. The psychometric properties of the SDIHW indicate future research value. Moderate internal consistency, reliability, content, and construct validity were demonstrated. Achieving a better understanding of the Hispanic woman's perception of herself as a sexual being will aid the clinician in the development of culturally sensitive interventions.

Actinomycotic splenic abscesses presenting with arthritis

An 18-month-old Caucasian female began with a high fever. She developed swelling in one finger and one toe. Abdominal ultrasound revealed multiple abscesses in her spleen. Multiple blood culture and splenic abscess aspirations grew no pathogens. She had transient response to multiple antibiotics and splenic abscess drainage, but fever returned along with subcutaneous nodules. Culture of splenic tissue from her second splenic drainage eventually grew one organism identified as Actinomyces naeslundii. Therapy with high dose penicillin followed by amoxicillin p.o. and total splenectomy led to complete recovery.

Construction of a homodimeric dihydrofolate reductase-thymidylate synthase bifunctional enzyme

A gene encoding a bifunctional homodimeric dihydrofolate reductase-thymidylate synthase (DHFR-TS) was constructed by destroying the stop codon of Escherichia coli dihydrofolate reductase (DHFR) and joining the coding sequences of the monofunctional enzymes by a five amino acid linker. The protein was designed to mimic features of active site proximity and electrostatics in the protozoan DHFR-TSs which are believed to be important in channeling of the DHFR substrate, H2folate, to TS. The genetically engineered catalytically active homodimeric bifunctional DHFR-TS was expressed, purified and characterized. The component activities of the purified bifunctional enzyme had kinetic properties similar to those of the monofunctional TS and DHFR, but unlike the authentic bifunctional enzymes from protozoa this enzyme did not kinetically channel dihydrofolate from DHFR to TS.

Once-daily gentamicin therapy for experimental Escherichia coli meningitis

In vitro and in vivo studies have demonstrated that the bacteriologic efficacy of once-daily aminoglycoside therapy is equivalent to that achieved with conventional multiple daily dosing. The impact of once-daily dosing for meningitis has not been studied. Using the well-characterized rabbit meningitis model, we compared two regimens of the same daily dosage of gentamicin given either once or in three divided doses for 24 or 72 h. The initial 1 h mean cerebrospinal fluid (CSF) gentamicin concentration for animals receiving a single dose (2.9 +/- 1.7 micrograms/ml) was threefold higher than that for the animals receiving multiple doses. The rate of bacterial killing in the first 8 h of treatment was significantly greater for the animals with higher concentrations in their CSF (-0.21 +/- 0.19 versus -0.03 +/- 0.22 log10 CFU/ml/h), suggesting concentration-dependent killing. By 24h, the mean reduction in bacterial titers was similar for the two regimens. In animals treated for 72 h, no differences in bactericidal activity was noted for 24, 48, or 72 h. Gentamicin at two different dosages was administered intracisternally to a separate set of animals to achieve considerably higher CSF gentamicin concentrations. In these animals, the rate of bacterial clearance in the first 8 h (0.52 +/- 0.15 and 0.58 +/- 0.15 log10 CFU/ml/h for the lower and higher dosages, respectively) was significantly greater than that in animals treated intravenously. In conclusion, there is evidence of concentration-dependent killing with gentamicin early in treatment for experimental E. coli meningitis, and once-daily dosing therapy appears to be at least as effective as multiple-dose therapy in reducing bacterial counts in CSF.

Randomized comparison of differing periods of twice-a-day triple therapy for the eradication of Helicobacter pylori

BACKGROUND

We assessed the efficacy, compliance, and tolerability of the twice-a-day triple therapy, amoxycillin, omeprazole, and clarithromycin, for Helicobacter pylori and studied the effect of treatment duration (7, 10 or 14 days) on these factors.

METHODS

One-hundred and fifty subjects with H. pylori infection documented by 13C-urea breath test were randomly assigned to a 7, 10 or 14-day course of amoxycillin 1 g b.d., omeprazole 20 mg b.d. and clarithromycin 500 mg b.d. Subjects returned at the end of therapy for pill count and assessment of side-effects. Subjects returned for a repeat 13C-urea breath test 4 weeks after the end of therapy.

RESULTS

Poor compliance (< 80% of medications taken) was seen in 0 subjects at 7 days, 6% at 10 days, and 10% at 14 days (P = 0.03 by chi 2 test for trend; difference for 7 vs. 14 days = 10%; 95% CI, -2% to 18%; P = 0.056). Intention-to-treat eradication rates were 86% at 7 days, 90% at 10 days and 92% at 14 days. Per-protocol eradication rates were 86% at 7 days, 91% at 10 days, and 95% at 14 days (P = 0.11; difference for 7 vs. 14 days = 9%; 95% CI, -2% to 21%; P = 0.17).

CONCLUSIONS

One week of twice-a-day amoxycillin, omeprazole and clarithromycin is well tolerated and provides a good rate of H. pylori eradication. Increasing the duration of therapy decreases compliance but has the potential to modestly improve efficacy if the patient takes the full complement of medication.

Peroxynitrite reaction with carbon dioxide/bicarbonate: kinetics and influence on peroxynitrite-mediated oxidations

Peroxynitrite is a strong oxidant produced in vivo as the reaction product of superoxide anion and nitric oxide (k approximately 5 x 10(9) M-1 s-1) and can be formed and mediate reactions in the extracellular environment. It has recently been reported that peroxynitrite and carbon dioxide react in a second-order process (S. V. Lymar and K. Hurst (1995) J. Am. Chem. Soc. 117, 8867-8868). Since one of the most abundant constituents of the extracellular milieu is bicarbonate anion (25 mM in plasma) which is in equilibrium with carbon dioxide (1.3 mM in plasma) we have further studied the kinetics of the reaction between peroxynitrite and carbon dioxide/ bicarbonate and the effect of bicarbonate on different peroxynitrite-mediated oxidations. The apparent second-order rate constant for the reaction is (2.3 +/- 0.1) x 10(3) M-1 s-1 at 37 degrees C and pH 7.4 and a pH-independent second-order rate constant of (5.8 +/- 0.2) x 10(4) M-1 s-1 at 37 degrees C was obtained considering peroxynitrite anion and carbon dioxide as the reacting species. The enthalpy and entropy of activation are delta H* = +10.7 +/- 0.8 kcal mol-1 and delta S* = -6.5 +/- 0.5 cal mol-1 K-1, respectively. The presence of bicarbonate had variable influence on peroxynitrite-mediated oxidations. While bicarbonate significantly enhanced peroxynitrite-mediated nitration of aromatics, it partially inhibited the oxidation of thiols, dimethylsulfoxide, oxyhemoglobin, and cytochrome c+2 and totally inhibited the hydroxylation of benzoate. Spontaneous chemiluminescence studies suggest the formation of bicarbonate radicals during the interactions of peroxynitrite with carbon dioxide/ bicarbonate. Our results support that peroxynitrite anion rapidly reacts with carbon dioxide to yield an adduct (ONOOCO2-) which can participate in oxidation and nitration processes, thus redirecting the primary reactivity of peroxynitrite.

"Platicas y merienda": reaching Spanish-speaking patients in an oncology setting

PURPOSE

The United States Hispanic population has tripled since the mid-1950s and is projected to be the largest growing segment of the population through the year 2000. The traditional support group model has not been effective in reaching this population. Healthcare professionals must become innovative to better understand and provide programs for Spanish-speaking cancer patients.

DESCRIPTION OF PROJECT

At the M.D. Anderson Cancer Center, a group program titled "Platicas y Merienda" was developed that derived from several group modalities: education, social, and peer support. The program is coordinated and facilitated by Spanish-speaking social workers and uses other professionals within the institution as speakers to promote a multidisciplinary approach to providing support services.

FINDINGS

Participants experienced an increased sense of social and emotional well-being, expanded their knowledge of health-related information, and became aware of other services and benefits available to them.

CLINICAL IMPLICATIONS

During this time of change in the healthcare environment, innovation in clinical practice and program development is necessary to address the needs of the growing Hispanic population.

Prospective evaluation of the macrolide antibiotic dirithromycin for the treatment of Helicobacter pylori

BACKGROUND

Macrolide antibiotics are active in vitro and in vivo against Helicobacter pylori. We assessed a newer macrolide, dirithromycin, for the treatment of H. pylori in two separate studies.

METHODS

Volunteers with H. pylori infection (by 13C-urea breath test) were randomly assigned to 2-week treatment regimens. Study 1: dirithromycin 500 mg q.d.s., dirithromycin 500 mg q.d.s. plus omeprazole 40 mg q.d.s., or dirithromycin 500 mg q.d.s. plus metronidazole 500 mg t.d.s. Study 2: dirithromycin 500 mg q.d.s. plus omeprazole 20 mg b.d., dirithromycin 1000 mg q.d.s. plus omeprazole 20 mg b.d., or amoxycillin 500 mg q.d.s. plus omepirazole 20 mg b.d. Four weeks after the completion of therapy a repeat 13C-urea breath test was done to assess for cure.

RESULTS

No patient taking dirithromycin alone (n = 6) or in combination with omeprazole (n = 26) achieved cure of their infection. Eradication of H. pylori was seen in one of seven patients taking dirithromycin plus metronidazole. Five of 10 patients taking omeprazole-amoxycillin dual therapy had their H. pylori infection cured (P = 0.0007 vs. patients taking dirithromycin plus omeprazole). Eleven (47%) of 32 patients taking dirithromycin alone or combined with omeprazole reported side-effects, but only two (6%) stopped therapy prematurely as a result of side-effects.

CONCLUSION

No subject taking dirithromycin alone or in combination with omeprazole had their H. pylori infection cured. Dirithromycin, in the regimen used, shows little promise in the treatment of patients with H. pylori infection.

Heterologous expression and characterization of the bifunctional dihydrofolate reductase-thymidylate synthase enzyme of Toxoplasma gondii

We have expressed catalytically active Toxoplasma gondii dihydrofolate-thymidylate synthase (DHFR-TS) and the individual TS and DHFR domains in Escherichia coli using the T7 promoter of pET-15b. DHFR-TS constituted approximately 10% of the total soluble cell protein and was purified using methotrexate-Sepharose chromatography to yield 10 mg of homogeneous DHFR-TS per liter of culture. The DHFR domain was recovered as insoluble inclusion bodies which could be unfolded and refolded to recover soluble, active enzyme. The TS domain was overexpressed as a soluble protein by growing the cells at 24 degrees C; this is the first report of the expression of an active TS domain from a bifunctional enzyme. The kcat and K(m) values for DHFR-TS are similar to those of other previously characterized protozoan DHFRs and TSs. The antimicrobial antifolates, TMP and Pyr, inhibit DHFR activity of the bifunctional protein in accord with their effects in crude enzyme preparations and in vivo systems. Kinetic parameters and Ki values for TMP and Pyr with the isolated DHFR domain were identical to the values for DHFR in the bifunctional enzyme. Evidence of kinetic channeling of the dihydrofolate product of TS to the DHFR domain in the bifunctional enzyme was obtained by kinetic and inhibition studies. Properties such as yield, stability, and activities of the recombinant T. gondii DHFR-TS provide clear advantages over other bifunctional DHFR-TSs as a model for future studies.